The invention relates to a brake lining for a disc brake, particularly for a pneumatically actuated disc brake for commercial vehicles, having a pressure plate and a lining material mounted on the pressure plate, and at least one return device that axially returns the brake lining after braking operations, provided on the pressure plate. The return device rests on a lining groove of the disc brake and carries out a tilting movement in the lining groove when braking operation occurs.
A lining of the generic type is disclosed in EP 0 534 987 B1. This lining has a pressure plate and a lining material mounted on the pressure plate, a flat spring being arranged at one of the outer edges of the pressure plate, which flat spring rests at the caliper side on a removable retaining element and, when assembled, is prevented from being detached by way of two holding clips.
This lining is particularly suitable for application in pneumatically actuated disc brakes, as are known, for example, from the product information document “Pneumatisch betätigte Scheibenbremse—Die Standardbremse für moderne Nutzfahrzeuge” [“Pneumatically actuated disc brakes—The standard brakes for modern commercial vehicles”] from Knorr-Bremse Systeme für Nutzfahrzeuge. A similar design is presented in the more recent EP 0 703 378 B1.
In the case of disc brakes, as are known, for example, from EP 703 378 B1, the sliding caliper and the brake carrier—on which the sliding caliper is displaceably guided—together form lining grooves, into which the brake linings are inserted from above.
When braking operations occur, the brake lining on the side of the brake caliper which is provided with a brake application device is first pressed against the brake disc. The subsequent sliding movement of the caliper then causes the brake lining arranged on the opposite side of the brake caliper to likewise be pressed against the brake disc. The brake linings in the lining grooves of the brake carrier are in the process pushed in the direction of the brake disc.
After the braking operation, the brake application unit, the caliper and the linings must be returned. A return spring of the brake application device, which brings about a spring force between the caliper and a cross brace of the application device, and therefore a relative displacement between these two components after the braking operation, serves to return the application unit.
On the other hand, in contrast to, for example, brake linings for drum brakes that retract from the brake drum, the brake linings for disc brakes are not generally retracted from the brake disc actively, since it is assumed that the brake linings are released from the brake disc again independently through vibration and the like.
However, in such a case there may be the problem that, under some circumstances, the brake caliper also has some preload from the flat springs acting as holding elements, which directly influences the return behavior of the brake caliper.
A large holding force brings about a correspondingly high preload on the brake caliper and can thus, under some circumstances, adversely affect the return process. A similar effect can occur with the brake linings. Incomplete retraction can lead to the brake linings grinding on the disc. Although this does not adversely affect safety, the grinding does however lead to faster brake lining wear and, therefore, increases the operating costs.
For the purpose of noise damping, it is known from DE 196 23 867 C2 to arrange rubber elements between a supporting element and the pressure plate on the tangential supporting surfaces of the pressure plate for the purpose of providing support in the lining groove of the brake carrier.
A supporting element for brake linings of disc brakes, which element is preloaded by the use of a spring, is also known from DE 196 23 867 C2 (see column 4, row 30 et seq. in this document). The supporting element also has the effect of a return element. This firstly leads to a tilting movement at the lining carrier groove when braking operations occur. The spring has a returning effect in the axial direction when the braking operation has ended. According to the knowledge of the present invention, however, the return movement is relatively undefined, on account of the relatively undefined force with which support is provided in the tangential direction.
Taking the generic prior art as a starting point, it is therefore an object of the invention to improve the return of the brake linings using simple structural mechanisms. If the brake caliper is in the form of a moveable caliper, that is to say of a sliding, floating or pivoting caliper, the return movement of the brake caliper should preferably also be assisted. The invention should, however, also be suitable in principle for disc brakes with fixed calipers.
The invention achieves this object by providing a return device having a tensioning device which acts in the tangential direction with a tensioning spring which, when the brake is not applied, elastically preloads the pressure plate in the tangential direction relative to a brake disc of the disc brake, that is to say in the direction of the lining groove, so that the return device rests tangentially on the lining groove in a preloaded state.
The tensioning device with the tensioning spring makes it possible for the tangential support of the return elements on the brake lining groove to be preset in a defined fashion, hence making it possible to obtain an accurately controlled return movement of brake lining and—if moveable—the brake caliper.
According to one embodiment, the return device has a return element which is moveably guided in a recess of the pressure plate, the tensioning spring preloading the return element tangentially in the direction of the lining groove. The return element rests on the lining groove.
A particularly good function of the return movement is achieved with this structural refinement.
The tensioning springs expediently rest between the return element and the pressure plate. According to a preferred, particularly reliable and therefore low-cost design, the tensioning spring is in turn formed particularly as a curved flat or wire spring, which engages with its ends in lateral lugs on each side of the recess for the return element, rests there and acts, with a central bulged region, on the return element.
In a particularly low-cost embodiment, the tensioning spring, the functions of the axial return spring and of the return and tensioning element, can alternatively be combined in a single element. This allows, by way of example, the tensioning spring to be formed in an uncomplicated manner as a singly or multiply curved inward flat or wire spring, which is fixed with both of its ends to the pressure plate and has a bulge which rests on the lining groove.
If wear occurs on the lining, the return elements and the lining in the lining groove are displaced.
For this purpose it is expedient if, according to a further preferred embodiment, the spring force of the tensioning spring is less than the frictional force between the lining guiding or supporting surfaces in the lining groove and the return elements.
The invention is particularly suitable for moveable brake calipers such as sliding or floating calipers. It is, however, also suitable in principle for fixed calipers, in which case it improves solely the return of the brake linings.
It is possible, depending on the design and type of brake, to provide the return devices at the brake linings on only one or on both sides of the brake disc.
Advantageous refinements are described and/or claimed herein.